Apparatus for investing dental casting patterns



April 3, 1934. D. w. PHILLIPS APPARATUS FOR INVESTING DENTAL CASTINGPATTERNS Filed March 3, 1932 aflz.

Patented Apr. 3, i 1934 UNITED STATES APPARATUS FOR INVESTING DENTALCASTING PAT-TEENS David W. Phillips, Chicago, 111.

Application March 3, 1932, Serial No. 596,447

7 Claims.

This invention relates to apparatus for making dental castings, andparticularly to improved means for investing a casting pattern in a bodyof investment.

An important object of the invention is to provide means for effectingabsorption of water from the body of investment to produce quick initialsetting of the latter after the pattern has become embedded therein,thereby materially re- 10 ducing the time required to prepare thefinished casting.

Other objects and advantages of the invention will be apparent from thefollowing detailed description, which, taken in connection with theaccompanying drawing, discloses a preferred embodiment thereof.

Referring to the drawing:

Fig. l isa top plan view of an investment container and a sprue holderconstructed in accord- 0 ance with the invention;

Fig. 2 is a broken vertical section through the improved container andholder assembly, the View being taken as indicated by line 2--2 of Fig.l;

, Fig. 3 is a perspective view. of the metal rim portion ofthe sprueholder which is adapted to receive an absorbent refill element;

Fig. 4is abottom plan view of the sprue-supporting refill: elementadapted to be removably secured withinthe metal rimpiece shown in Fig.

3; and

Fig. dis a detail section of a modified form of absorbentsprue-supporting element.

Briefly, the invention consists in making the sprue holder of. amaterial which is capable of quickly absorbing water from the mass ofmoist investment when'it is brought into contact with the latter.. Thisrapid removal of water from the investment reduces the time required forthe setting of. the mass, and thereby speeds up the 40 investingoperation. Also the rapid absorption of water from the investment afterthe pattern has become imbedded thereintends to produce smoothercastings, for the reason that ittends to provide a drier, denserinvestment about all surfaces of the pattern, thereby eliminating excessive moisture which tends to cause surface imperfections in thefinished. casting. Although the sprue holder may be formed entirely ofan absorbent material, I prefer to construct it in i t o parts, onepartconsisting of a metal rim piece which is received .on the container,and the other part, which carries. the pattern,,consisting of anabsorbent refill element, which is removably secured within the rim.piece.

Referringto the drawing, the numeral B'd'esignates a tubular containerfor receiving. a body or mass of investment 9. The lower end of thecontainer 8 is closed' by a rubber end cap 11, the marginal rim portionof which is turned upwardly, as indicated at 12; to form a water- 00tight seal with the side Walls of the container. The use of the rubberend cap for closing one'end of the container is particularly desirablein water-bath technique, since it prevents seepage of water into thebody of investment when the container is immersed. Because of itselasticity, the cap 11 will yield under pressure of the expandinginvestment to permit full setting expansion of the latter and at thesame time it will maintain a water-tight seal with the end of thecontainer. The use of the rubber end cap is also desirable, for thereason that it may be readily snapped around the ends of containers ofvarious sizes and shapes.

The sprue holder illustrated in Figs. 1-4 com- 7 prises a rim piece l3,and an absorbent sprue supporting refill element 14. Rim piece 13, whichis preferably made of metal, serves as a means for supporting element14" in proper position relative to the investment container. Saidrimpiece 13 comprises: a central body portion 15, which is tapered inwardlyto engage the sides of the cone-shaped element 14; and a top flangepiece 16, which is formed as an integral part of body portion 15, andwhich is adapted to rest on the top edge of container 8 when the holderis positioned thereon, as shown in Fig; 2. Refill element l4,as'previously noted,.is cone-shaped so that when it is positioned on theinvestment container it willpr'oject into the mass of investment toform, when removed therefrom, a corresponding cone-shaped cavity in thebody of investment, said cavity serving asa crucible for'receivingmolten metal in the subsequent casting operation. A sprue 17, whichsupports a pattern 18 in the investment, is removably anchored inelement 14' by means of a body of wax. 19 which serves to anchor theupper end of the sprue in an axially disposed cavity formed in element14.

Element 14 is removably secured in rim piece l3'by means of tonguemembers 21 which project inwardly fromflangelfiv of said rim piece, saidtongue members" being received in notches 22 formed in the top" edgeportions of element 14, said notches being spaced to correspond to thespacing of tongue. members 21. As will be noted from Figs. 3 and 4,tongue members'ZI are pitched downwardly, and the rim portions of refillelement 14" adjoiningnotches 22 are bevelled as indicated at 23. It willbe evident that when element 14 is positioned on rim piece 13, withnotches 22 disposed opposite tongue members 21, it may be dropped intoposition, whereupon a turning of said element in a counter-clockwisedirection relative to rim piece 13, viewing Fig. 1, will cause tonguemembers 21 to wedge upon bevelled surfaces 23 thereby securely anchoringelement 14 in position in rim piece 13.

Refill element 14 is made of a water-absorbent material, so that whenplaced on the investment container it will extract water from the bodyof investment to produce quick setting of the mass. Various materialsmay be used for forming element 14. Among the materials which aresuitable for use for this purpose, there may be mentioned set plaster ofParis, set hydrocal, and various pressed fibrous materials such asabsorbent paper, absorbent cloth, and the like.

The manner of use of the absorbent sprue-supporting refill element willbe apparent from Fig. 2. After the investment has been prepared it isplaced in container 8, the lower end of which has previously been closedby rubber end cap 11. A double layer of moistened asbestos paper 24 isinserted as a lining for the walls of the investment container inaccordance with the usual practice. Refill element 14 is then secured inplace in rim 13, after which wax pattern 18 is placed on sprue 17 andthe latter is anchored in position in element 14. The entire spruesupporting assembly is then lowered onto the investment container untilflange 16 engages the upper edge of container 8. The refill element 14,being absorbent in character, rapidly extracts Water from the body ofinvestment, thereby bringing about an almost immediate initial settingof the entire mass of investment. The time required for the investingoperation is thus materially reduced. Also by reason of absorption ofwater by element 14, there is obtained a drier, denser investment aboutthe surfaces of the pattern which enables the production of smoothercastings. The greater the proportion of water present in a mix of inlayinvestment, the rougher will be the surfaces of the finished casting.This is due to the fact that a large proportion of water in the mixtends to cause roughness in the surfaces of the set mass of investmentafter the water and wax have been burned out of the set investment. Onthe other hand, an almost immediate set of the investment preventsroughness in castings caused by any slight vibration of the mass ofinvestment in the container before it sets. For example, slightvibration caused by a lathe running on the work bench will cause waterto separate in the investment near the pattern surfaces before settingoccurs. Upon burning out of the wax, this water is removed and theunevenness thus produced in the investment surfaces causes acorresponding roughness in the surfaces of the finished castings.

After final setting of the investment, the sprue holder is removed fromthe container, this being effected by imparting a twisting movement torim 13 which effects separation of rim 13 and element 14 from the setmass of investment. The body of wax 19, which holds sprue 17 in element14, yields during this twisting operation to allow separation of thesprue from the holder. The tongue members 21 should be so related to thesurfaces 23 of element 14 that when the holder is twisted fromengagement with the container, these tongue members will wedge moretightly onto the surfaces 23 to prevent element 14 from becomingloosened in rim 13. In order to prevent turning of the set body ofinvestment in container 8 during removal of the sprue holder, I make theupper end of said container hexagonal in shape, as shown in Figs. 1 and2. The hexagon-shaped portion need extend over but a small portion ofthe length of container 8 and is formed as a continuation of thecylindrical side walls, the joining of these portions being indicated byline 25 in Fig. 2.

If desired, the sprue holder may be made of a single piece of absorbentmaterial, as indicated in Fig. 5. In this form the holder, which isindicated generally by the numeral 26, includes a main cone-shaped bodyportion 27 and a peripheral rim portion 28, the latter serving as asupport for the holder when it is placed on the top of container 8. Thecomplete unit is made of an absorbent material of the type hereinbeforespecified. The sprue 29 is removably secured in the body portion of theholder by means of a mass of wax 31 in the same manner as described forthe form shown in Figs. 1-4.

When using the form of holder shown in Fig. 5,

some difliculty may be encountered in placing the holder on thecontainer, due to the fact that water may be so quickly absorbed fromthe portions of investment near the upper edge portions of the ring thatthe mass becomes somewhat dry and does not allow the holder to be freelypushed into place. By the use of rim piece 13 this difiiculty asavoided, since water is not rapidly absorbed from the portion of theinvestment lying near the upper edge of the container, so that theseportions remain somewhat moist and allow the holder to be easily placedin position on the container.

In Fig. 2 I have shown the use of an absorbent disc 32 which isinterposed between end cap 11 and the body of investment 9. This disc isintended to fit loosely within container 8, being held in place by endcap 11. It may be made of any one of the absorbent materialshereinbefore specified, and affords additional means for effecting rapidextraction of water from the mass of investment to reduce the settingtime. The disc 32 may be used in conjunction with the absorbent sprueholder shown in Fig. 2, or may be used in conjunction with the regularall-metal sprue supporter. While the bulk of the water absorption takesplace through the absorbent sprue holder, because of its greater mass,the absorbing action of disc 32 is appreciable and its use tends tofurther reduce the time required for eifecting initial setting of theinvestment.

The foregoing detailed description has been given for clearness ofunderstanding only, and no unnecessary limitations should be understoodtherefrom, but the appended claims should be construed as broadly aspermissible in view of the prior art.

What I regard as new and desire to secure by Letters Patent is:

1. In an apparatus for investing dental casting patterns, including aninvestment container, a pattern-supporting sprue, and a holder thereforadapted to be placed upon one end of the container, a closure for theother end of the container, comprising a flexible cap adapted to fitupon the lower end of the container and having an annular flange adaptedto grip the container wall, said cap providing a water-tight closure andbeing extensible under pressure of the investment against said cap.

2. Apparatus for investing a casting pattern comprising a tubularcontainer for holding a mass of investment, a pattern-supporting sprue,a crucible-forming holder for said sprue adapted to be placed on one endof said container, said holder being formed of a material capable ofabsorbing Water from the investment to thereby produce quick initialsetting of the mass after the pattern has become embedded therein, andmeans affording a closure for the other end of the container, saidlast-mentioned means including a body of absorbent material for removingwater from the investment to further aid in reducing the setting time ofthe mass.

3. Apparatus for investing a casting pattern comprising in combinationwith an investment container, a pattern-forming sprue, and a holdertherefor adapted to be placed upon one end of the container, a removablecap for the other end of the container, and a layer of absorbentmaterial positioned in said cap and adapted to contact with the body ofthe investment when the cap is in place on the container.

4. Apparatus for investing a casting pattern comprising an investmentcontainer open at one end, the other end thereof being closed by aremovable cap forming a water-tight seal with the body of the container,said cap being formed of an elastic material adapted to yield underpressure of the expanding investment, a pattern-supporting sprue, acrucible-forming holder for said sprue adapted to be placed on the openend of the container, said holder being formed of a material capable ofabsorbing water from i the investment to thereby produce quick initialsetting of the mass after the pattern has become embedded therein, and alayer of absorbent material interposed between said end cap and theadjacent body of investment, said absorbent layer serving to removewater from the investment to further aid in reducing the setting time ofthe mass.

5. Apparatus for investing a casting pattern comprising an investmentcontainer open at one end, the other end thereof being closed by aremovable cap forming a water-tight seal with the body of the container,said cap being formed of an elastic material adapted to yield underpressure of the expanding investment, a pattern-supporting sprue, acrucible-forming holder for said sprue adapted to be placed on the openend of the container, said holder comprising a rim piece for engagingthe end of the container, and a spruesupporting refill element removablysecured within said rim piece, said supporting element being formed of amaterial capable of absorbing water from the investment to therebyproduce quick initial setting of the mass after the pattern has becomeembedded therein, and a layer of absorbent material interposed betweensaid end cap and the adjacent body of investment, said absorbent layerserving to remove water from the investment to further aid in reducingthe setting time of the mass.

6. In an apparatus for investing dental casting patterns, including aninvestment container, a crucible-former arrangeable upon an end of theinvestment container and adapted to be pressed against the body of theinvestment contained therein, the portion of said crucible-former whichcontacts said investment being formed of waterabsorbent material capableof extracting water from a mix of investment within the container tothereby produce quick setting of the investment and the production ofsmooth castings.

'7. In an apparatus for investing dental casting patterns, including aninvestment container, a crucible-former arrangeable upon an end of theinvestment container, said crucible-former comprising a rim piece forengaging the end of thecontainer, and a sprue-supporting refill elementremovably secured Within said rim piece, said element being formed of anabsorbent material capable of extracting water from a mix of theinvestment within the container.

DAVID W. PHILLIPS.

